Craving Earth

If dirt, as William James put it, is matter out of place, then thedirtiest dirt of all is the kind you put where you’re absolutely not supposedto: in your mouth. We teach children not to eat dirt even before they can talk;conversely, telling someone to eat dirt is a powerful expression of contempt, away of demoting them from human to animal. Yet as Sera L. Young explains in herquirkily informative book Craving Earth:Understanding Pica, eating dirt—in particular, certain kinds of dry,crumbly clay, as well as other non-food substances like uncooked starch, chalk,and ice—is a very widespread human practice, and always has been. Pica, as this behavior is known—thename comes from the Latin word for “magpie”—is especially commonamong pregnant women.

This has been recognized since ancient times: Hippocrates, the5th-century BC Greek physician, noted that pregnant women often had cravingsfor earth or charcoal, and a classic Indian poem describes a pregnant queen who”set her heart upon clay in preference to all other objects of taste.”Today, Young reports, Americans with pica buy boxes of chalk at Walmart, orbags of ice (the cubes at the Sonic fast-food chain seem to be especiallypopular), or even order prime Georgia dirt over the Internet.

Yet the stigma attached to eating dirt is so strong that few peoplewill readily admit to it. One of Young’s most fascinating chapters, “Dismissaland Damnation,” shows that European scientists who observed pica amongAfrican or Asian peoples described it as a degenerate vice. An Amazonianexplorer who noticed the practice among “the natives” cited it asevidence that they “appear to be sunk in an abyss of moral filth anddepravity from which nothing but a strong tide of European immigration can savethem.” Among the illustrations in CravingEarth are chilling images of the iron masks that American slaveholders usedto prevent their slaves from eating dirt; in Jamaica, slaves alleged to havedied from pica had their corpses decapitated as a warning to others.

This stigma depends on the idea that pica is bothunnatural and unhealthy. But is it? That’s the question Young, a medicaldoctor, sets out to answer in CravingEarth by reviewing the scientific literature on pica. Operating on theassumption that a behavior could not be so widespread and apparentlyinstinctive unless it was adaptive in some way, Young considers two hypotheses.The first is that pica is a way for people to get nutrients missing from theirdiet, especially iron. This idea seems to be supported by the observedcorrelation between dirt-eating and anemia: in fact, a Roman writer mentionedthe connection between “pale complexion” and “a morbid appetitefor earth” some 2,000 years ago.

Yet Young goes on to show that the correlation is ambiguous: addingiron to the diet of a person with pica does not seem to eliminate her cravings,nor does eating earth seem to add iron to the blood. On the contrary, one studyshows that eating dirt reduces the body’s ability to absorb iron, raising thepossibility that pica actually causes anemia, instead of curing it.

More plausible, though still not definitively proven, is the idea thatdirt-eating helps to protect the body from toxins and pathogens. Clay, Youngexplains, is a perfect natural filter, binding poisons and bacteria to itsporous surface; indeed, clay is commonly used in water filters like Brita, andin many anti-diarrhea medicines. (Kaopectate is named after kaolin, a kind ofclay that used to be its active ingredient.) It is suggestive, then, that mostpeople who engage in geophagy—from the Greek for “dirt eating”—preferclayey soils. What’s more, the populations that seem most prone to pica—pregnantwomen and people in tropical regions—are also the most vulnerable to poisonsand parasites. Without more study, Young concludes, we can’t yet say exactlywhat pica means or what harm it may do. In the meantime, Craving Earth offers the best account we have of this oddlyfascinating subject.


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